The present invention relates to an elastic roller, and more particularly it relates to an elastic roller used in the paper feed mechanism of an OA (office automation) business machine, such as a laser beam printer, copying machine, facsimile device or ATM.
As for elastic rollers used in the paper feed mechanisms of laser beam printers, copying machines, facsimile devices, and ATMs, since abrasion resistance is required, rubbers having a high mechanical strength, such as natural rubber, urethane rubber, chloroprene rubber, and Norsorex rubber are in general use.
As for the aforesaid elastic rollers, besides abrasion resistance, which is one of the characteristics required in paper feed operation, the following may be mentioned.
First, it is required that when the elastic roller slips relative to paper, it should not contaminate the paper.
Secondly, when the elastic roller is subjected to a low temperature condition, curing or crystallization should not take place on it.
Thirdly, it is required that the elastic roller should have a high friction coefficient so that it does not slip relative to the paper.
Fourth, since an electronic photograph device, such as a copying machine, has a corona charge therein to effect charging for image transfer, ozone of high concentration is produced in the device. Therefore, it is required that the elastic roller should have ozone resistance so as not to be attacked by ozone.
Fifthly, in recent years, reduction in the size of said OA business machines has advanced and, unlike the case of large-sized machines, periodical maintenance, and exchange of elastic rollers are becoming less frequent. Therefore, it is also required that they should have durability, free from aging or deterioration.
In the requirements described above, particularly, an elastic roller which is superior in ozone resistance is desired in view of the generation of ozone of high concentration in the interior of an electric photograph machine, such as a copying machine. Chloroprene rubber, urethane rubber and silicone rubber are desired because of their high ozone resistance, but when such factors as low hardness, winterization and price are considered, EPDM rubber is the best.
However, though EPDM rubber has good durability against aging and deterioration, it has low mechanical strength and is inferior in abrasion resistance; therefore, EPDM rubber is low in durability for use in machine parts such as paper feed rollers, and hence it has not been used so frequently. Further, in order to decrease hardness, process oil is used, but EPDM rubber itself has a drawback that it hardly mixes with process oil and its processability is poor.